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The Optimal Catenary Mooring Arrangement for Least Sensitivity to Single Mooring Line Broken in Semi-Submersible Platform

Seyed Abbassian, Mohammad Reza | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51186 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Tabeshpour, Mohammad Reza
  7. Abstract:
  8. The discovery of oil and gas resources in deep waters led to the invention of various platforms adapted to these waters. As the search for oil and gas resources is advanced to deep water, it is impossible to use fixed platforms in these depths. Hence, the idea of using floating platforms that can be used in deep waters has been increasingly considered. An option for the exploration and extraction of offshore oil resources is semi-submersible platforms. Under wave, wind, and current forces, a floating structure moves from its initial location. Types of mooring systems are used to maintain the position of the platform. During the life of a platform, mooring lines may be damaged under conditions. A mooring line Failure transfers the static and dynamic forces resulting from the structure response and environmental conditions to the remaining mooring lines. In this research, the Amir Kabir semi-submersible platform was modeled in Ansys Aqwa. First, the platform is placed in waves with a height of 1 meter and various periods. At this stage, the RAOs in different degrees of freedom is attained. Afterward, the platform is moored by four catenary mooring lines configurations in the software. In these mooring configurations, the angles between two lines of lines in each cluster are 15, 30, 45 and 60 degrees. In the following, in three wave directions, 0, 45 and 90 degrees, random waves are plotted in the form of the JONSWAP wave spectrum in accordance with the conditions of the Caspian Sea. The four mooring configurations are investigated in two cases: The failure in initial Position and the Failure during the storm. in each of these cases, four individual mooring lines in each configuration are broken and examined. Then, after a time history analysis in all these conditions, the response of the six degrees of freedom is compared with each other. According to the results, with the failure of each mooring lines, the configurations are not effective in the heave response. But in the other five degrees of freedom, results indicate that the 15-degree configuration has a better performance
  9. Keywords:
  10. Semisubmersible Platform ; Caspian Sea ; Catenary Mooring Line ; Mooring Failure ; JONSWAP Wave Spectrum

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